Amplification of the genes coding for rRNA (rDNA) occurs in the oocytes of various species of organisms. Recent work indicates that rDNA is replicated during amplification by a rolling circle mechanism. In organisms where it has been studied, the genes coding for 5S RNA (5S DNA) are not amplified. The main objectives of this proposal have been and still are to determine whether amplification represents a generalized phenomenon associated with oogenesis; to determine the extent of diversity which exists in regard to the degree of amplification and the nature of amplified DNA; and to correlate this diversity with differences in the organization of amplified DNA. Emphasis will be placed on the last objective. To this end, molecular mapping techniques will be applied to somatic and ovarian rDNA of the house cricket, Acheta domesticus. We wish to determine the molecular size and organization of DNA sequences coding for rRNA, spacer sequences, and the entire rDNA repeating unit. Moreover, we would like to determine whether amplification in A. domesticus occurs via a rolling circle intermediate. Other workers have reported amplification of DNA in chromomeres of A. domesticus which apparently do not contain rDNA. Do these contain 5S DNA and is 5S DNA amplified? Finally, do vertebrates other than fish and amphibians simplify their rDNA? Is rDNA amplified in the uninucleolate oocytes of mammals? An answer to the last question is relevant to man because of the similarities between oogenesis in man and in other mammals.